Objectives: Gefitinib, a tyrosine kinase inhibitor (TKI) targeting epidermal growth factor receptor (EGFR), shows excellent clinical benefit in treating advanced non-small-cell lung cancer (NSCLC). The aim of this study was to compare the efficacy and toxicity of gefitinib as first-line therapy and second-line therapy for advanced lung adenocarcinoma patients with positive exon 21 (L858R) or exon 19 deletion of EGFR  mutation.
Methods: We retrospectively analyzed the clinical data of 60 EGFR -mutated advanced lung adenocarcinoma patients from July 2011 to November 2015 who have received oral gefitinib 250 mg once daily. Gefitinib was taken until disease progression, intolerable toxicity or death.
Results: After a median follow-up of 792 days, one death had occurred. Among the 59 patients who survived, 17 patients progressed. Overall, the median progression-free survival (mPFS) was 10 months (95% confidence interval [CI]: 7.53–12.46 months, p <0.05). The response rate (RR) and disease control rate (DCR) were 33.33% and 71.66%, respectively. However, there was longer mPFS in the first line-therapy than that in the second-line therapy: in the first-line gefitinib therapy, mPFS was 12 months among 41 patients (95% CI: 9.58–14.41 months, p <0.05), and in the second-line therapy, mPFS was 7 months among 19 patients (95% CI: 1.31–12.68 months, p <0.05). Furthermore, in subgroup analyses examining different EGFR  mutation types, we noted that mPFS was significantly longer for patients with exon 19 deletion than for those with positive exon 21 in both the first-line therapy and second-line therapy.
Conclusion: Patients with advance lung adenocarcinoma who were selected by positive exon 21 or 19 deletion mutations had significantly longer mPFS in the first-line therapy than that in the second-line therapy when treated with gefitinib. EGFR  mutation types may influence the response to gefitinib therapy.
Keywords: gefitinib, epidermal growth factor receptor, tyrosine kinase inhibitor, lung adenocarcinoma